Now as for your trip from Michigan to Halifax...
If you have a particular reason to see Toronto or Montreal on your way through, then that's great! They are both viberant cities with more than enough to keep you entertained for days. If you're planning the trip for July, try to hit Montreal during the "Just for Laughs" Festival. We've been there a few times and it really is a great time. Toronto always has lots happening throughout the summer as well.
However, if you're just wanting a nice ride to and from, then I would go further north, at least as far as Hwy. 7 or even better further north and come across the Blue Water Bridge in Port Huron, MI / Sarnia, ON and go north along the east side of Lake Huron and under Geogian Bay, making your way further north to Hunstville and ride through Algonquin Park along Hwy. 60 over to Renfrew and down through our Nation's Capital - Ottawa. From there I would head into Quebec staying north of Montreal and plan for a stay in Mont-Tremblant. Continue staying well north of the St. Lawrence, working your way towards Quebec City. This wonderful old city you can spend days in and never tire of. After that at some point you will have to cross the St. Lawrence heading for New Brunswick before Nova Scotia. In New Brunswick make sure you stop to see the highest tides in the world at the Bay of Fundy. When in Nova Scotia a must ride is in the northern part doing the Cabot Trail... And make sure you do it counterclockwise so that you are always riding on the waterside of the road for the best views.
On your way back if time permits head south to Bar Harbor, Maine wonderful seaside community prior to heading east on Rte. 2 through Maine, New Hampshire, Vermont, picking up Rte. 3 through New York.
Sounds like an amazing trip and I hope this helps.
Enjoy!
